AU2004296413B2

AU2004296413B2 - Reflective optical sensor for bill validator

Info

Publication number: AU2004296413B2
Application number: AU2004296413A
Authority: AU
Inventors: Sergiy Androsyuk; Dmitro Baydin; Mykhaylo Bazhenov; Gennadiy Gaponyuk; Oleksandr Lukonin; Yuriy Rusakov
Original assignee: Crane Canada Co
Current assignee: Crane Canada Co
Priority date: 2003-12-12
Filing date: 2004-12-10
Publication date: 2009-12-17
Anticipated expiration: 2024-12-10
Also published as: CN1902663B; EP1704536A1; US20050127305A1; WO2005057505A1; JP2007514219A; CA2453229A1; US7271398B2; AU2004296413A1; EP1704536A4; CN1902663A

Description

WO 2005/057505 PCT/CA2004/002103 TITLE: REFLECTIVE OPTICAL SENSOR FOR BILL VALIDATOR FIELD OF THE INVENTION 5 The present invention relates to bill validators, having an optical sensor means for measuring the reflectance and transmittance of paper bills as they move past the optical sensor. The sensor includes a radiation emitter which also acts to direct reflected radiation to 10 a photodetector. This sensor may also be used as common reflective sensor for detection of various index marks with relatively small space dependence. BACKGROUND OF THE INVENTION 15 Bill validators used in vending machines and the like typically utilize various styles of reflective optical sensors to obtain measurements from an inserted bill to determine authenticity, denomination and location. Typically, the bill is transported past at 20 least one photosensor, having a light-emitting diode (LED) and photodetector (photodiode or phototransistor). Some factors that adversely affect the bill measurements include the following: inserted bills are of 25 different denominations, cleanliness and quality; bill may be creased or crumpled, and the bill location and inclination across passageway may strongly vary.In addition, the output power of LED can vary due to age and/or ambient conditions. Furthermore, there are normal 30 production variations in LED optical power output and detector sensitivity, which can lead to sensors having varying current and voltage requirements in order to operate effectively. In order to partially offset these factors, optical sensor measurements are taken over a 35 large dynamic range. As power of LED and sensitivity of - 1- WO 2005/057505 PCT/CA2004/002103 photodetector are limited, the optical efficiency should be high to improve the performance of the sensors. In the art, many embodiments of reflective optical 5 sensors are known. The simple sensors comprise at least one photo emitter and one photo detector with relatively wide spatial diagrams (U.S. Patent 4,348,656; U.S. Patent 4,628,194; U.S. Patent 5.222.584; U.S. Patent 5,476,169; U.S. Patent 5,692,067; U.S. Patent 5,751,840; U.S. Patent 10 5,855,268; U.S. Patent 5,889,883; U.S. Patent 5,909,503; U.S. Patent 5,960,103). Such sensors have low optical efficiency and their output signal strongly depends on bill location and inclination across passageway. The space required to mount the sensors (footprint) slightly 15 exceeds the total area of the emitters and detectors. To improve optical efficiency, many sensors mount the emitters and detectors at an angle to one another and converging on the bill surface (U.S. Patent 4,041,456; 20 U.S. Patent 4,628,194; U.S. Patent 4,973,851; U.S. Patent 5,420,406; U.S. Patent 5,467,405; U.S. Patent 5,483,069; U.S. Patent 5,918,960; U.S. Patent 5,992,601; U.S. Patent 6,028,951; U.S. Patent 6,073,744). These sensors require special optical heads, receptacles etc. The footprint for 25 these sensors significantly exceeds the total area of emitters and detectors due to the various mountirig and carrying paths. Even with this more complicated design, the output signal from these sensors strongly depends on bill location and inclination across passageway. 30 Advanced sensors in addition to plurality of LED's and photo detectors comprise various focusing, light guiding and reflecting elements, including fiber optic "fish tails" and splitters (U.S. Patent 5,308,992; U.S. 35 Patent 5,381,019; U.S. Patent 5,616,915; U.S. Patent - 2 - 3 6,044,952; U.S. Patent 6,104,036; U.S. Patent 6,163,036; U.S. Patent 6,188,080; U.S. Patent 6,359,287; U.S. Patent 6,392,863). These sensors are more complicated, large and expensive, require special optical parts and often require additional alignment during validator assembly. The output signal of these 5 advanced sensors continues to be largely dependent on bill location and inclination across passageway. Some special optical sensors conduct bill scanning by means of LED's and detectors arrays with special lenses or by direct TV image or light beam scanning 10 (U.S. Patent 4,179,685; U.S. Patent 4,197,584; U.S. Patent 4,293,776; U.S. Patent 6,363,164). This technology is expensive and is not suitable for mass production and utilization. Some optical shadow on a bill may occur with the majority of prior art 15 sensors because of bill inclination, illumination or observation. It is preferable to provide a simple reflective space efficient sensor having high optical efficiency for bill examination and other applications. 20 The present invention addresses a number of the disadvantages described above with respect to the prior art sensors. SUMMARY OF THE INVENTION According to one aspect of the present invention, there is provided a 25 validation device for assessing the authenticity of bills comprising a bill passageway, an optical sensing arrangement to one side of said passageway and opening onto said passageway for directing radiation onto a bill as it moves past said optical sensing arrangement and for receiving radiation reflected from said 30 bill, an arrangement for processing an output signal of said optical sensing arrangement and producing an evaluation signal, and 4 an evaluation system that uses said evaluation signal and based thereon makes a prediction of the authenticity of the bill; said optical sensing arrangement includes a light emitting diode having at least one photodetector adjacent a base thereof, said light emitting diode having 5 a light transmitting case thereabout and positioned to act as a light guide for radiation received at an end of said case opposite said photodetector. The case of the light emitting diode device may include a convex end which faces the bill passageway and acts as a lens to direct emitted radiation 10 onto the bill and to receive and direct radiation impinging on the convex lens through the case to the photodetector. The light transmitting case may have a generally flat transparent base adjacent the photodetector and the photodetector is located below the base. 15 The convex end of the case may be immediately adjacent the bill passageway. The convex end of the case may be of a width greater than the spacing 20 between the convex end and the center line of the bill passageway. The light emitting diode may be a directional emitter directing emitted radiation generally through the convex end of the case. 25 The light emitting diode may be designed to emit ultraviolet radiation. The validation device may also comprise an ultraviolet absorbing thin film filter between light emitting diode base and photo detector. 30 The validation device may also include band-pass or rejection colored thin film filters between light emitting diode base and said photo detectors.

5 The light emitting diode may be designed as a multicolor multi chip light emitting diode. According to a further aspect of the present invention, there is provided a 5 validation device having an optical sensing arrangement, said optical sensing arrangement includes a light emitting diode having at least one photodetector adjacent a base thereof, said light emitting diode having a light transmitting case thereabout and positioned to act as a light guide for radiation received at an end of said case opposite said photodetector; 10 said validation device including a processing arrangement for processing an output signal of said photodetector. According to a still further aspect of the invention, there is provided a method of document examination comprising: 15 perpendicular narrow-beam illumination of a part of the surface of the document by means of a transparent body bulb ultraviolet light emitting diode; collection of the mirror and diffuse reflected light and fluorescent light from said illuminated document part by means of a convex end of said light emitting diode which acts as a lens; 20 transmission of said collected light through the light emitting diode body to a photo detector positioned adjacent to said light emitting diode base; filtering of said transmitted light with absorption and/or band pass filters between said light emitting diode and photo detector; and processing of an output signal of said photodetector for document 25 identification and validation. Comprises/comprising and grammatical variations thereof when used in this specification are to be taken to specify the presence of stated features, integers, steps or components or groups thereof, but do not preclude the 30 presence or addition of one or more other features, integers, steps, components or groups thereof.

6 Several embodiments of the present invention will now be described by way of example with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS 5 Preferred embodiments of the invention are shown in the drawings, wherein: FIG 1 is an enlarged side view of optical sensor for bill ultraviolet testing; FIG. 2 is an exploded enlarged perspective assembly view of optical sensor for bar-code reading and bill edge detection; 10 FIG.3 is a block diagram of hardware component processing of signals in ultraviolet optical sensor; FIG. 4 is a typical signal of genuine bill ultraviolet scanning in FIGURE 1 embodiment; FIG. 5 is a typical signal of counterfeit bill ultraviolet scanning in FIGURE 1 15 embodiment; and FIG. 6 is a typical signal of bar code scanning in FIGURE 2 embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical sensor 2 shown in Figure 1 is positioned for emitting radiation 20 to eradiate the bill 12. The surface characteristics of the bill alter the radiation which is reflected from the bill and returned to the optical sensor. The bill 12 is transported through the bill passageway 20 defined by an exterior wall 13 and a light transparent wall 11. 25 The optical sensor 2 has a light emitting diode (LED) 4, positioned to one side of the passageway 20 and located immediately adjacent the transparent wall 11. The light emitting diode 4 has a transparent case 6 with a generally cylindrical portion terminating at one end in the convex lens portion 10 and closed at the other end by the quasi planar base 14. The case 6 is preferably of a plastic 30 or other light transmitting material. Radiation produced by the LED 4 passes through the plastic case. Generally centered within the case is a luminous chip 16 centrally located in a non light transmitting concave recess 18. The luminous chip 16 is connected by a pair of leads 22 to a power source. Radiation from the 7 luminous chip 16 generally passes in a parallel manner through the convex lens 10 of the plastic case 6. The radiation produced by the LED is generally through the end of the LED and produces a narrow beam of radiation for eradiating the bill 12. The radiation produced by the LED strikes the bill and depending upon the 5 characteristics of the bill, is reflected from the surface thereof. A portion of this reflected radiation strikes the convex lens 10 of the LED and passes therethrough and is guided to the base 14 of the LED and through the base to photodetectors 25 and 26 located exterior to the based of the LED. 10 From the above, it can be appreciated that the casing of the LED acts as a light guide for directing reflected radiation from the bill, which strikes the convex end of the plastic case of the LED to the photodetectors located below and outside of the LED. Both the LED 4 and the photodetectors 25 and 26 are mounted on the printed circuit board 7 and the signals from the photodetectors 15 are processed by circuitry on the printed circuit board. The diameter of the cylindrical walls 8 of the LED are of the order of 5 mm and the radiation produced by the LED is generally of this width and it is generally directed in a perpendicular manner towards the surface of the bill 12. The bill 12 20 is spaced from the convex end 10 of the LED up to approximately 3.5 mm. It can thus be appreciated that the beam of radiation is wide relative to the distance of separation from the LED to the bill. The convex end 10 serves to focus reflected radiation back onto the photo diodes 25 and 26. With this arrangement, most of the outgoing radiation which serves to illuminate the bill surface and is reflected 25 therefrom, is collected by the LED convex lens and transmitted to the photodetectors. It has generally been found that this arrangement results in a reflected signal which is maintained within a much tighter tolerance even with changes in location of the bill in the passageway, the condition of the bill and the inclination thereof. 30 It has been found that the reflected signal is typically in the range of 60% to 85% of the produced signal. Thus the optical signal would change up to approximately 30% under bill displacement across the passageway of up to 2 8 mm. The beam of radiation produced by the LED is relatively narrow, typically between 8 and 12 degrees. The close positioning of the LED to the bill and the use of the LED as a wave guide to return the reflected radiation, results in a signal which is less sensitive to bill inclination in the passageway. 5 The embodiment shown in Figure 1 also includes a filter arrangement 28 between the base 14 and the photodetector 25. This preferably is an ultraviolet absorbing film filter. With this arrangement, the LED is preferably a 5 mm bulb ultraviolet LED under the trademark HUUV-5102L sold by Roithner Lasertechnic 10 or general equivalent. Thus the bill 12 is exposed to ultraviolet radiation with the reflected signal and any luminous signals of the bill returning through the LED to the photodetectors 25 and 26. Photodetector 26 receives the entire signal whereas the signal received by photodetector 25 is absent any ultraviolet portion. 15 The embodiment of Figure 1 produces a signal at photodetector 26 which is a result of all light radiation striking the detector. In contrast, photodetector 25 is a similar signal but with the UV component removed. Ambient light can also influence photodetectors, however, the positioning of the photodetectors beneath the LED and the plastic casing of the LED acting as a light transmitting guide to 20 the photodetectors, reduces problems associated with ambient light. Furthermore, ambient light is generally associated with the bill passageway 20 and the structure of the optical sensor locates the photodetectors, a significant distance away from the passageway. In this way, the photodetectors are not as sensitive to ambient light in the passageway. 25 Optical sensor 2 is located in its own casing having its own transparent wall 11 which forms part of the passageway. This forms a module with the printed circuit board and the LED located within a housing typically formed of a non transparent plastic with the exception of the transparent wall 11. The 30 elongate form of the optical sensor advantageously uses the LED to not only produce radiation for illuminating the bill but it also uses the LED as a light guide for directing the reflected radiation to the photodetectors located beneath the LED. Opposite passageway wall 13 is made from white non fluorescent ABS 9 plastic. Reflection signal from this wall is used for apparatus self calibration when bill is absent in passageway. Figure 2 is a perspective view of an alternate embodiment of the optical 5 sensor. The optical sensor 100 is positioned adjacent the transparent wall 110 in the bill passageway 120 having an exterior wall 113. The bill 112 or other document is shown having a bar code 115. The optical sensor 100 includes a printed circuit board 107 having a photodetector 105 mounted thereon. The photodetector 105 is exposed to the reflected radiation which will pass back 10 through the LED 101. This LED has a transparent outer casing 104 made up of a cylindrical portion 106, a convex end portion 108, and a generally planar transparent base 109. The LED includes its own light source 111 within the LED which is designed to direct radiation out through the convex end 108. Connectors 130 and 132 support the light source 111 generally centered within the LED and 15 connected and provides power to it from the printed circuit board 107. A non transparent shield 140 covers the end of the LED and has a slit opening 150 for allowing the radiation to pass therethrough. As can be appreciated, some of the radiation will be reflected off the end wall 142 of the end 20 cap, however, this will be a constant signal back to the photodetector 105 where various arrangements can be used to reduce this radiation component. A portion of the produced radiation will pass through the slot 150 and will provide a narrow radiation source for illuminating the individual bars of the bar code 115 as they pass by the optical sensor. The signal which is returned to the photodetector 25 through the LED 104 acting as a wave guide and through the transparent base 109 to the photodetector will vary in accordance with the bar code 115. This arrangement has proven to provide a very effective means for reading of the bar code and providing good quality results with the various possible misorientations of the bar code within the passageway 120. As can be appreciated, the optical 30 sensor 100 and the transparent wall 110 can be integrated into a single module which is inserted in a suitable port in the wall of the bill passageway of a validator or other sensing device.

10 The arrangement of Figure 2 is also effective in identifying a bill edge. This is particularly useful for detecting a leading or trailing edge of a bill as it moves past the sensor. 5 With the embodiment of Figure 2, the beam of light eradiating the bill has a small angle of divergence so the light divergence on the bill surface does not exceed 0.3 mm. A red LED LTL2F3VEKNT by LITE-ON Inc. and IC photo detector S7184 or S7815 by HAMAMATSU Co. can be used in the bar-code detector. 10 Figure 3 is a block diagram of hardware components used to process signals in an ultraviolet optical sensor. Light 10 reflected from the bill surface is received by photodiode 6 (integral light detector) and is received by photodiode 5 (detector of visible light) after passing through UV absorbing filter 4. Signal Uint, 15 proportional to visible light intensity, proceeds from the output 20 of amplifier 17. This signal describes the fluorescent properties of the bill paper and dyes. Signal Uint + Uuv), proportional to total light outgoing from bill, proceeds from the output of amplifier 18 to resistor adder 19. Under equal transfer constants of amplifiers 17, 18 and resistors R in adder unit 19 at the output 21, outgoing signal 1/2[Uint 20 (Unt + Uuv)] = -1/2 Uuv is developed. This signal describes the ultraviolet reflection of bill surface. Signals from outputs 20, 21 are used in a processor module for bill authorization and discrimination. For example, a large value of Uint signal indicates that bill may be counterfeit - i.e. a photocopy on a wood-based paper. 25 Figure 4 is a typical signal Uint of genuine bill ultraviolet scanning in Figure 1 embodiment. Scanning speed is about 300 mm/sec. Point 22 indicates the moment of bill leading edge passing by optical sensor. Point 23 indicates the moment of bill trailing edge passing by optical sensor. The signal at 24 (bill is 30 absent in passageway) is caused by back wall 13 reflectance of blue components of illuminating light and by light reflected from all transparent interfaces (about 6% on each) - boundaries between LED and air, air and wall 11, wall 11 and air. The signal at 24 is used for apparatus self calibration. Signal Uint between points 22 11 and 23 is caused by bill paper and dyes fluorescence and reflectance of blue components of illuminating light. Figure 5 is a typical signal Uint of a counterfeit bill (similar to previous 5 genuine bill) ultraviolet scanning in Figure 1 embodiment. Scanning speed is about 300 mm/sec. Points 22 - 24 indicate the same as in previous illustration. Bands 25 indicate strong fluorescence from leading and trailing bill borders. Band 26 indicates the strong fluorescence from paper bill surface in the watermark zone. Signal Uint strongly differs on genuine and counterfeit bills and is easily 10 used in the processor module to identify counterfeit bills. Figure 6 is a typical signal of bar code scanning in Figure 2 embodiment. The slit 15 in opaque cap 14 is 5 mm length and 0.4 mm wide. Scanning speed is about 300 mm/sec. This arrangement provides a good spatial resolution with 15 bar distance and width less then 0.5 mm. The present invention is described herein in the context of a banknote application used in a verification device, automatic cash machine or other bills handling device, in a bank, postal facility, supermarket, casino or transportation 20 facility. However, it is appreciated that the embodiments shown and described herein may also be useful for checking other objects, particularly flat objects, such as cards, films, paper sheets and paintings. The checking device may be stationary or portable, battery powered or powered by connection to an electric outlet. 25 It is appreciated that various features of the invention, which are, for clarity, described in the contexts of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, 30 may also be provided separately or in any suitable combination. Although various preferred embodiments of the present invention have been described herein in detail, it will be appreciated by those skilled in the art, 12 that variations may be made thereto without departing from the spirit of the invention or the scope of the appended claims.

Claims

1. A validation device for assessing the authenticity of bills comprising a billpassageway, an optical sensing arrangement to one side of said passageway and 5 opening onto said passageway for directing radiation onto a bill as it moves past said optical sensing arrangement and for receiving radiation reflected from said bill, an arrangement for processing an output signal of said optical sensing arrangement and producing an evaluation signal, and 10 an evaluation system that uses said evaluation signal and based thereon makes a prediction of the authenticity of the bill; said optical sensing arrangement includes a light emitting diode having at least one photodetector adjacent a base thereof, said light emitting diode having a light transmitting case thereabout and positioned to act as a light guide for 15 radiation received at an end of said case opposite said photodetector.

2. A validation device as claimed in claim 1 wherein said light transmitting case of said light emitting diode includes a convex end facing said bill passageway which acts as a lens to direct emitted radiation onto said bill and to receive and direct reflected radiation impinging on said convex end through said 20 case to said photodetector.

3. A validation device as claimed in claim 2 wherein said light transmitting case of said light emitting diode has a generally flat bottom adjacent said photodetector and said photodetector is located below said flat bottom.

4. A validation device as claimed in claim 3 wherein said convex end of said 25 light transmitting case of said light emitting diode is immediately adjacent said bill passageway.

5. A validation device as claimed in claim 4 wherein said convex end of said light transmitting case of said light emitting diode is of a width greater than a spacing between said convex end and a centerline of said bill passageway. 14

6. A validation device as claimed in claim 1 wherein said light emitting diode is a directional emitter directing emitted radiation through an end of said light transmitting case of said light emitting diode.

7. A validation device as claimed in claim 6 wherein said light emitting diode 5 is designed to emit ultraviolet radiation.

8. A validation device as claimed in claim 7 additionally comprising an ultraviolet absorbing thin film filter located between said light emitting diode and said photo detector.

9. A validation device as claimed in claim 6 wherein said light emitting diode 10 is designed to emit white light.

10. A validation device as claimed in claim 9 further comprising a band-pass or rejection colored thin film filters located between said light emitting diode and said photo detector.

11. A validation device as claimed in claim 6 wherein said light emitting diode 15 is designed as multicolor multi chip light emitting diode.

12. A validation device having an optical sensing arrangement, said optical sensing arrangement includes a light emitting diode having at least one photodetector adjacent a base thereof, said light emitting diode having a light transmitting case thereabout and positioned to act as a light guide for radiation 20 received at an end of said case opposite said photodetector; said validation device including a processing arrangement for processing an output signal of said photodetector.

13. A validation device as claimed in claim 12 wherein said light emitting diode includes a non transparent shield member at an end of case opposite said 25 photodetector, said shield member having a slit therein for allowing a thin beam of radiation to pass therethrough and to allow reflected radiation to pass through said slit to said case for guiding to said photodetector. 15

14. A validation device as claimed in claim 13 used for reading of bar codes moved past said optical sensing arrangement.

15. A method of document examination comprising: perpendicular narrow-beam illumination of 'a part of the surface of the 5 document by means of a transparent body bulb ultraviolet light emitting diode; collection of the mirror and diffuse reflected light and fluorescent light from said illuminated document part by means of a convex end of said light emitting diode which acts as a lens; transmission of said collected light through the light emitting diode body to 10 a photo detector positioned adjacent to said light emitting diode base; filtering of said transmitted light with absorption and/or band pass filters between said light emitting diode and photo detector; and processing of an output signal of said photodetector for document identification and validation. 15

16. A method as claimed in claim 15 wherein said light emitting diode is an ultraviolet light emitting diode and; said filtering of the transmitted light includes ultraviolet absorption and/or band-pass filters and detecting the filtered transmitted light with the photo detector; and including 20 separate processing of steady and alternate photo signal components from said photo detector for bill identification and validation.

17. A method as claimed in claim 15 for sequential evaluation of optical characteristics of a bill wherein said light emitting diode is a multicolor multichip light emitting diode that provides sequential perpendicular narrow-beam 25 illumination of said bill part with varicolored light; and wherein said processing of said output signal includes sequential detection and processing of said varicolored light components for bill identification and validation. 16

18. A method as claimed in claim 15 wherein said light emitting diode emits ultraviolet light and said document is a banknote.

19. A method as claimed in claim 15 for detecting bar code on a substrate wherein said light emitting diode produces monochrome light and only a portion of 5 the produced monochrome light passes through a narrow, slight sized to produce a narrow beam of monochrome light; moving the document in a direction generally perpendicular to the narrow beam of monochrome light to illuminate a bar code surface of the document; and processing of an alternating output signal component from the photo 10 detector for bar code identification.

20. A validation device for assessing the authenticity of bills, a validation device having an optical sensing arrangement, or a method of document examination, substantially as hereinbefore described with reference to the accompanying drawings. 15 CRANE CANADA CO WATERMARK PATENT & TRADE MARK ATTORNEYS P27232AU00